The invention covers a device for breaking-out scrap pieces during punching of material in sheet or web form, such as paper, cardboard or similar material, by means of two counter-rotating rolls, the lower of which is a smooth cylinder, while the upper is equipped with breaking-out tools and is displaced relative to the lower cylinder in the direction in which the material is advancing.
Such devices are designed to remove scrap pieces of different size and configuration created during the punching of folding boxes or similar items from the sheet or web of material. These scraps are connected to the workpiece by single fibres of material and by scrap bridges created at the impact points of the punching tool. Force must therefore be brought to bear on the scraps to separate the bridges during breaking-out operations.
To date, breaking-out of scrap by rotating devices has been accomplished primarily by picking up the scrap pieces with needles (DT-AS 1,511,048 and many others). It has also been suggested that scrap pieces may be held back and removed from the sheet material with the application of a partial vacuum (DT-AS 1,144,576). Additionally, a device is known in which the top roll is equipped with breaking-out projections which can be compressed in a longitudinal direction. The top roll runs on a plane different from that of the lower roll and vertical to the direction of movement of the material, so that the scrap pieces to be broken out come in contact with successive breaking-out projections staggered over the periphery of the top roll (DT-OS 1,611,617).
All these prior devices serve their purpose provided that the scrap pieces are sufficiently large to be subject to the intended effect. All known prior art devices, however, fail as soon as the scrap pieces are small, e.g., a circular surface of 5 millimeters in diameter or strips of 4 millimeters in width. Picking up the scrap pieces with needles will result in interruptions of the breaking-out process when the single scraps are so small that penetration of the needle causes the material to burst and thus the scraps can no longer be firmly held and removed. The vacuum approach, which can only be a partial vacuum, does not have sufficient holding power for small scraps to ensure a smooth removal of the pieces. Besides, these two devices are not well suited for breaking-out larger scrap pieces, which show a certain resistance to deflection, such as pieces of strong cardboard or corrugated board. A special device has been designed for this purpose, according to DT-OS 1,611,617. However, it fails to securely clamp the scrap pieces at the beginning of the breaking-out process and thus is unable to smoothly remove the smaller scraps too.
However, the breaking-out of small or long, narrow scraps is of the highest importance economically, as similar scraps are produced in large numbers during punching of folding boxes, and their reliable removal is decisive for the profitability of the entire punching operation.
The present invention solves this problem by making the distance between the centers of the cylindrical elements or rolls smaller than the sum of the radii of said rolls including the radial distance of the tool assembly in the outer rest position of the break-out tool. The tool assemblies are designed for radial spring action of a scrap engaging tool element in a way which is basically already known.
This construction of the cylindrical rolls results in the scrap pieces being securely held proximate the contact point of the material web with the lower roll, and in the scrap pieces being clamped between the radially springing breaking-out tool and the lower roll. There is no opportunity for evasion of even the smallest piece of scrap.
For the effects of this invention it is preferable to mount the radially springing or compressible break-out tools for adjustment in a peripheral or circumferential direction about the top cylindrical element or roll on disks, which also can be adjusted in an axial direction and are easily exchanged.
This form of construction permits presetting of the break-out tools in accordance with the different locations, shapes and configurations of the scrap pieces.
To transport the work pieces from the breaking-out device and evenly guide them during the breaking-out operation, it is advisable to mount rollers between the disks forming the rolls and carrying the break-out tools. These rollers engage and press the work pieces still remaining in the material plane against the lower roll.
It is further preferable to form the lower roll of easily exchanged cylinder sections, between which bars are adjustably mounted for movement in the direction of the roll axis and tangential to the circumference of the roll.
These bars feed the sheets of material or sections of web tangentially against the lower roll and serve as support for the work pieces remaining on the working surface during breaking-out operations.
An important additional feature of the device of the present invention consists in providing the shafts of the breaking-out device in the punching machine with graded scales and further to provide a separate tool presetting device with a similarly graded scale. This makes it unnecessary to tie up the punching machine for adjustments or resetting of the breaking-out device for new patterns. The disks with the breaking-out tools can, with the aid of these graded scales, be mounted on the upper shaft, and the cylinder sections can be mounted on the lower shaft in a very short period of time and in the exact same position that the breaking-out tools and cylinder sections had assumed in the presetting device.
The present invention offers the following advantages: scrap pieces of all sizes, especially those of very small size, are smoothly broken out by means of the rotating breaking-out device, of the present invention. The apparatus is further distinguished by its simple drive mechanism, a low encumbrance and its suitability for high material speeds. Furthermore, it is not necessary for the sheet of material or web to be stopped for the breaking-out operation. The break-out tools are simple and can be mounted closely to each other; they are universally applicable to various bolster plates. The device does not require the making of special parts to accomodate the changing form and configuration of the scrap pieces. The sets of tools can be preset in a separate device and mounted in the breaking-out device in a very short time.